Devices for intrabody delivery of molecules and systems and methods utilizing same

ABSTRACT

A device for controlled release of molecules is provided. the device including: (a) a device body having at least one reservoir therein for containing the molecules, the at least one reservoir being formed with a barrier impermeable to the molecules thereby preventing release thereof from the at least one reservoir; and (b) at least one acoustic transducer being attached to, or forming a part of, the device body, the at least one acoustic transducer being for converting an acoustic signal received thereby into an electrical signal, the electrical signal leading to barrier permeabilization and therefore release of the molecules from the at least one reservoir.

FIELD AND BACKGROUND OF THE INVENTION

[0001] The present invention relates to a device for intrabody deliveryof molecules, to a method and system of utilizing same and to a methodof fabricating same. More particularly, embodiments of the presentinvention relate to a drug delivery device which utilizes an acoustictransducer for generating an electrical activation signal from anacoustic signal received thereby.

[0002] The efficacy of drug treatment is oftentimes dependent upon themode of drug delivery.

[0003] Localized drug delivery is oftentimes preferred since ittraverses limitations associated with systemic drug delivery includingrapid drug inactivation and/or ineffectual drug concentrations at thesite of treatment. In addition, in some cases, systemic drug deliverycan lead to undesired cytotoxic effects at tissue regions other thanthat to be treated.

[0004] Since localized intrabody delivery of medication is central toefficient medical treatment attempts have been made to design andfabricate intrabody delivery devices which are capable of controlled andlocalized release of a wide variety of molecules including, but notlimited to, drugs and other therapeutics.

[0005] Controlled release polymeric devices have been designed toprovide drug release over a period of time via diffusion of the drug outof the polymer and/or degradation of the polymer over the desired timeperiod following administration to the patient. Although these devicesenable localized drug delivery, their relatively simple design islimited in that it does not enable accurate and controlled delivery ofthe drug.

[0006] U.S. Pat. No. 5,490,962 to Cima, et al. discloses the use ofthree dimensional printing methods to make more complex devices whichprovide release over a desired time frame, of one or more drugs.Although the general procedure for making a complex device is described,specific designs are not detailed.

[0007] U.S. Pat. No. 4,003,379 to Ellinwood describes an implantableelectromechanically driven device that includes a flexible retractablewalled container, which receives medication from a storage area via aninlet and then dispenses the medication into the body via an outlet.

[0008] U.S. Pat. Nos. 4,146,029 and 3,692,027 to Ellinwood discloseself-powered medication systems that have programmable miniaturizeddispensing means.

[0009] U.S. Pat. No. 4,360,019 to Jassawalla discloses an implantableinfusion device that includes an actuating means for delivery of thedrug through a catheter. The actuating means includes a solenoid drivenminiature pump.

[0010] Since such devices include miniature power-driven mechanicalparts which are required to operate in the body, i.e., they mustretract, dispense, or pump, they are complicated and subject to frequentbreakdowns. Moreover, due to complexity and size restrictions, they areunsuitable for delivery of more than a few drugs or drug mixtures at atime.

[0011] U.S. Pat. Nos. 6,123,861 and 5,797,898 both to Santini, Jr., etal. disclose microchips devices which control both the rate and time ofrelease of multiple chemical substances either in a continuous or apulsatile manner. Such microchip devices employ a reservoir cap which isfabricated of a material that either degrades or allows the molecules todiffuse passively out of the reservoir over time or materials thatoxidize and dissolve upon application of an electric potential. Releasefrom the microchip device can be controlled by a preprogrammedmicroprocessor, via a radiofrequency (RF) activation signal, or bybiosensors.

[0012] Although the microchip device described by Santini, Jr., et al.presents substantial improvements over other prior art devices, itsuffers from several inherent limitations which will be described indetail hereinbelow.

[0013] There is thus a widely recognized need for, and it would behighly advantageous to have, a delivery device and methods offabricating and utilizing same which device can be used for accurate andtimely delivery of a drug or drugs within a body tissue region devoid ofthe above limitation.

SUMMARY OF THE INVENTION

[0014] According to one aspect of the present invention there isprovided a device for controlled release of molecules comprising: (a) adevice body having at least one reservoir therein for containing themolecules, the at least one reservoir being formed with a barrierimpermeable to the molecules thereby preventing release thereof from theat least one reservoir; and (b) at least one acoustic transducer beingattached to, or forming a part of, the device body, the at least oneacoustic transducer being for converting an acoustic signal receivedthereby into an electrical signal, the electrical signal leading tobarrier permeabilization and therefore release of the molecules from theat least one reservoir.

[0015] According to an additional aspect of the present invention thereis provided system for localized delivery of molecules within the bodycomprising: (a) an intrabody implantable device including: (i) a devicebody having at least one reservoir therein for containing the molecules,the at least one reservoir being formed with a barrier impermeable tothe molecules thereby preventing release thereof from the at least onereservoir; and (ii) at least one acoustic transducer being attached to,or forming a part of, the device body, the at least one acoustictransducer being for converting an acoustic signal received thereby intoan electrical signal, the electrical signal leading to barrierpermeabilization and therefore release of the molecules from the atleast one reservoir; and (b) an extracorporeal unit for generating theacoustic signal.

[0016] According to another aspect of the present invention there isprovided a method of delivering molecules to a specific body region, themethod comprising: (a) implanting within the body region a deviceincluding: (i) a device body having at least one reservoir thereincontaining the molecules, the at least one reservoir being formed with abarrier impermeable to the molecules thereby preventing release thereoffrom the at least one reservoir; and (ii) at least one acoustictransducer being attached to, or forming a part of, the device body, theat least one acoustic transducer being for converting an acoustic signalreceived thereby into an electrical signal, the electrical signalleading to barrier permeabilization and therefore release of themolecules from the at least one reservoir; and (b) extracorporeallyirradiating the body with an acoustic signal thereby causing thesubsequent release of the molecules from the at least one reservoir.

[0017] According to further features in preferred embodiments of theinvention described below, the device further comprising a cathode, andan anode, whereas the electrical signal generates an electric potentialbetween the cathode and the anode leading to permeabilization of thebarrier and release of the molecules from the at least one reservoir.

[0018] According to still further features in the described preferredembodiments the anode is attached to or forms at least a part of thebarrier.

[0019] According to still further features in the described preferredembodiments the electrical signal directly generates the electricpotential between the cathode and the anode.

[0020] According to still further features in the described preferredembodiments the device further comprising a power source for generatingthe electric potential between the cathode and the anode upon receivingthe electrical signal from the at least one acoustic transducer.

[0021] According to still further features in the described preferredembodiments the at least one acoustic transducer serves as an acousticswitch.

[0022] According to still further features in the described preferredembodiments permeabilization of the barrier is effected by at leastpartial disintegration thereof.

[0023] According to still further features in the described preferredembodiments a type or duration of the electrical signal controls adegree of permeabilization of the barrier and thus an amount of themolecules released.

[0024] According to still further features in the described preferredembodiments the device includes a plurality of reservoirs.

[0025] According to still further features in the described preferredembodiments the device includes a plurality of acoustic transducers.

[0026] According to still further features in the described preferredembodiments each of the plurality of acoustic transducers generates anelectrical signal which leads to permeabilization of a barrier of acorresponding reservoir of the plurality of reservoirs.

[0027] According to still further features in the described preferredembodiments each of the plurality of acoustic transducers is capable ofconverting an acoustic signal of a distinct frequency or frequenciesinto the electrical signal.

[0028] According to still further features in the described preferredembodiments the plurality of reservoirs are for containing differenttypes of molecules, different amounts of molecules, or combinationsthereof.

[0029] According to still further features in the described preferredembodiments the molecules are drug molecules.

[0030] According to still further features in the described preferredembodiments the at least one acoustic transducer includes: (i) a cellmember having a cavity; (ii) a substantially flexible piezoelectriclayer attached to the cell member, the piezoelectric layer having anexternal surface and an internal surface, the piezoelectric layerfeaturing such dimensions so as to enable fluctuations thereof at itsresonance frequency upon impinging of an external acoustic wave; and(iii) a first electrode attached to the external surface and a secondelectrode attached to the internal surface.

[0031] According to still further features in the described preferredembodiments the device includes a plurality of reservoirs eachcontaining molecules of a specific type and each capable of releasingthe molecules upon provision of an acoustic signal of a specificfrequency or frequencies, such that a frequency content of the acousticsignal determines a type of the molecules released.

[0032] According to an additional aspect of the present invention thereis provided a device for controlled drug release comprising: (a) adevice body including at least one reservoir being for containing aprodrug form of a drug, the at least one reservoir being formed with abarrier impermeable to the prodrug thereby preventing release thereoffrom the at least one reservoir; and (b) at least one acoustictransducer being attached to, or forming a part of the device body, theat least one acoustic transducer being for converting an acoustic signalreceived thereby into an electrical signal, the electrical signalleading to a conversion of the prodrug into the drug, the drug beingcapable of traversing the barrier thereby releasing from the at leastone reservoir.

[0033] According to yet an additional aspect of the present inventionthere is provided a system for localized delivery of molecules withinthe body comprising: (a) an intrabody implantable device including: (i)a device body including at least one reservoir being for containing aprodrug form of a drug, the at least one reservoir being formed with abarrier impermeable to the prodrug thereby preventing release thereoffrom the at least one reservoir; and (ii) at least one acoustictransducer being attached to, or forming a part of the device body, theat least one acoustic transducer being for converting an acoustic signalreceived thereby into an electrical signal, the electrical signalleading to a conversion of the prodrug into the drug, the drug beingcapable of traversing the barrier thereby releasing from the at leastone reservoir; and (b) an extracorporeal unit for generating theacoustic signal.

[0034] According to still further features in the described preferredembodiments a type or duration of the electrical signal controls adegree of the conversion and thus an amount of the drug formed andreleased

[0035] According to still further features in the described preferredembodiments the device includes a plurality of reservoirs and aplurality of acoustic transducers, each of the plurality of acoustictransducers generates an electrical signal which leads to the conversionof the prodrug to the drug contained in a corresponding reservoir of theplurality of reservoirs.

[0036] According to still further features in the described preferredembodiments the plurality of reservoirs are for containing differenttypes of prodrugs, different amounts of prodrugs, or combinationsthereof.

[0037] According to still an additional aspect of the present inventionthere is provided a method of fabricating a device for controllablerelease of molecules, the method comprising: (a) providing a substrate;(b) configuring the substrate with at least one reservoir; (c) cappingthe at least one reservoir with a cap material which acts as animpermeable barrier to the molecules, the material becoming permeable tothe molecules following generation of an electrical potential in oraround the at least one reservoir; and (d) providing an inlet port forfilling the at least on reservoir with the molecules, the inlet beingsealable following the filling, thereby generating the device forcontrollable release of molecules.

[0038] According to still further features in the described preferredembodiments the method further comprising the step of: (e) attaching to,or fabricating within, the substrate, at least one acoustic transducer,the at least one acoustic transducer being for generating an electricalsignal from an acoustic signal received thereby, the electrical signalleading to generation of the electrical potential in or around the atleast one reservoir.

[0039] According to still further features in the described preferredembodiments the at least one acoustic transducer includes: (i) a cellmember having a cavity; (ii) a substantially flexible piezoelectriclayer attached to the cell member, the piezoelectric layer having anexternal surface and an internal surface, the piezoelectric layerfeaturing such dimensions so as to enable fluctuations thereof at itsresonance frequency upon impinging of an external acoustic wave; and(iii) a first electrode attached to the external surface and a secondelectrode attached to the internal surface.

[0040] According to still further features in the described preferredembodiments step (b) is effected by etching the substrate.

[0041] The present invention successfully addresses the shortcomings ofthe presently known configurations by providing a device, system andmethod for efficient intrabody delivery of molecules such as drugs aswell as a method of manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention is herein described, by way of example only, withreference to the accompanying drawings. With specific reference now tothe drawings in detail, it is stressed that the particulars shown are byway of example and for purposes of illustrative discussion of thepreferred embodiments of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

[0043] In the drawings:

[0044]FIG. 1 is a cross sectional view of a general configuration of thedevice of the present invention;

[0045] FIGS. 2-3 illustrate cross sectional views of a prior arttransducer element utilizable by the device of the present invention;

[0046]FIG. 4 illustrates a “direct activation” configuration of thedevice of the present invention;

[0047]FIG. 5 illustrates an “indirect activation” configuration of thedevice of the present invention;

[0048]FIG. 6 is a schematic diagram illustrating an acoustic switchutilizable by the device of the present invention;

[0049]FIG. 7 is a black box diagram of a drug delivery system accordingto the teachings of the present invention; and

[0050]FIG. 8 is schematic diagram illustrating a control circuitry ofthe acoustic switch illustrated in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] The present invention is of a device, system and method which canbe used for localized intrabody delivery of molecules. Specifically, thepresent invention can be used to release molecules such as drugs withina specific body region using an acoustic activation signal provided fromoutside the body.

[0052] The principles and operation of the present invention may bebetter understood with reference to the drawings and accompanyingdescriptions.

[0053] Before explaining at least one embodiment of the invention indetail, it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is capable of other embodiments or of beingpracticed or carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein is for the purposeof description and should not be regarded as limiting.

[0054] Referring now to the drawings, FIG. 1 illustrates the device forcontrolled release of molecules, which is referred to herein as device10.

[0055] Device 10 includes a device body 12 having at least one reservoir14 formed therein for containing the molecules to be delivered.

[0056] Preferably, device body 12 includes a plurality of reservoirs 14(four shown in FIG. 1) each being configured for containing therapeuticmolecules such as drugs and/or diagnostic molecules such as dyespreferably in a solution or as a suspension. Reservoirs 14 can be ofvarious dimensions depending on the molecule type and quantity to bedelivered therefrom.

[0057] Device body 12 can be of a planar shape, spheroidal shape or anyshape suitable for intrabody implantation and delivery of moleculesstored thereby. Reservoirs 14 can be formed within a surface of devicebody 12 or within an interior volume thereof, provided moleculesreleased therefrom can disperse into a medium surrounding device 10.

[0058] The dimensions of device 10 are limited by the site ofimplantation and delivery, the quantity of drugs or drugs to bedelivered thereby, and the specific components used thereby for drugrelease activation.

[0059] Reservoirs 14 can be formed within device body 12 using anymethod known in the art including, but not limited to, etching,machining and the like. Alternatively, device body 12 may be pre-formedwith reservoirs 14 by, for example, casting or milling techniques.

[0060] Device body 12 is fabricated from a material which is impermeableto the molecules to be delivered and to the surrounding fluids, forexample, water, blood, electrolytes or other solutions. Examples ofsuitable materials include ceramics, semiconductors, biologicalmembranes, and degradable and non-degradable polymers; biocompatibilityis preferred, but not required.

[0061] For in-vivo applications, non-biocompatible materials may beencapsulated in a biocompatible material, such as polyethyleneglycol orpolytetrafluoroethylene-like materials, before use. One example of astrong, non-degradable, easily etched substrate that is impermeable tothe molecules to be delivered and the surrounding fluids is silicon.

[0062] Alternatively, device body 12 can also be fabricated from amaterial which degrades or dissolves over a period of time intobiocompatible components such as Polyvinyl Alcohol (PVA). Thisembodiment is preferred for in vivo applications where the device isimplanted and physical removal of the device at a later time is notfeasible or recommended, as is the case with, for example, brainimplants. An example of a class of strong, biocompatible materials arethe poly(anhydride-co-imides) discussed by K. E. Uhrich et al.,“Synthesis and characterization of degradablepoly(anhydride-co-imides)”, Macromolecules, 1995, 28, 2184-93.

[0063] Reservoir 14 is formed (capped) with a barrier 16 which isimpermeable to the molecules to be delivered. As such barrier 16 servesfor preventing molecules contained within reservoir 14 from releasinginto the surrounding medium when device 10 is implanted within the body.

[0064] Reservoir 14 can be filled with molecules of interest eitherprior to capping with barrier 16 or following such capping. In thelatter case, reservoir 14 also includes an inlet port 18, which servesfor filling reservoir 14 with molecules of choice following fabricationof device 10. Inlet port 18 is designed to be sealable followingfilling, such that accidental drug release therefrom does not occur.

[0065] Device 10 further includes at least one acoustic transducer 20.Acoustic transducer 20 can be attached to, or it can form a part of,device body 12. Acoustic transducer 20 serves for converting an acousticsignal received thereby into an electrical signal. The electrical signalgenerated by transducer 20 is preferably rectified via a full orhalf-bridge rectifier into a DC current signal. The converted electricalsignal can be used to directly or indirectly release the moleculesstored in reservoir 14 as described hereinbelow.

[0066] According to a preferred embodiment of the present invention, theelectrical signal generates (directly or indirectly) an electricalpotential within reservoir 14.

[0067] To this end, device 10 further includes at least one pair ofelectrodes 21, which are preferably positioned within reservoir 14 andwhich serve for providing the electrical potential therein.

[0068] According to one preferred embodiment of the present invention,the electrical potential converts the molecules stored within reservoir14 into an active and barrier permeable form.

[0069] For example, the molecules contained within reservoir 14 can beprovided as large aggregates which are unable to traverse barrier 16which can be, in this case, a size selective membrane. Upon provision ofthe electrical potential the molecules disaggregate into smaller activeunits which are able to diffuse out of reservoir 14 through barrier 16.

[0070] According to another preferred embodiment of the presentinvention, the electrical potential leads to permeabilization of barrier16 and subsequent release of the molecules from reservoir 14.

[0071] For example, the electrical potential generated by electrodes 21can cause the partial or full disintegration of barrier 16 and as suchthe release of the molecules from reservoir 14.

[0072] In such a case, barrier 16 can be composed of a thin film ofconductive material that is deposited over the reservoir, patterned to adesired geometry, and function as an anode 22. The size and placement ofcathode 23 depends upon the device's application and method of electricpotential control.

[0073] Conductive materials capable of dissolving into solution orforming soluble compounds or ions upon the application of an electricpotential, include, but are not limited to, metals such as copper, gold,silver, and zinc and some polymers.

[0074] Thus, according to this configuration of device 10, when anelectric potential is applied between anode 22 and cathode 23, theconductive material of the anode above the reservoir oxidizes to formsoluble compounds or ions that dissolve into solution, exposing themolecules to be delivered to the surrounding medium.

[0075] Alternatively, the application of an electric potential can beused to create changes in local pH near barrier 16 thereby leading todissolving of barrier 16 and release of the molecules.

[0076] Still alternatively, the application of an electric potential canbe used to create changes in the net charge of barrier 16 or the netcharge or solubility of the molecules thereby enabling barrier 16traversing.

[0077] In any case, the molecules to be delivered are released into thesurrounding medium by diffusion out of or by degradation or dissolutionof the release system. The frequency and quantity of release can becontrolled via the acoustic signal received by acoustic transducer 20 asis further described hereinbelow.

[0078] According to a preferred embodiment of the present invention andas specifically shown in FIGS. 2-3, acoustic transducer 20 includes atleast one cell member 22 including a cavity 24 etched or drilled into asubstrate and covered by a substantially flexible piezoelectric layer26. Attached to piezoelectric layer 26 are an upper electrode 28 and alower electrode 30 which are connectable to an electronic circuit.

[0079] The substrate is preferably made of an electrical conductinglayer 32 disposed on an electrically insulating layer 34, such thatcavity 24 is etched substantially through the thickness of electricallyconducting layer 32.

[0080] Electrically conducting layer 32 is preferably made of copper andinsulating layer 34 is preferably made of a polymer such as polyimide.Conventional copper-plated polymer laminate such as Kapton™ sheets maybe used for the production of transducer 20. Commercially availablelaminates such as Novaclad™ may be used. Alternatively, the substratemay include a silicon layer, or any other suitable material.Alternatively, layer 32 is made of a non-conductive material such asPyralin™.

[0081] An insulating chamber 36 is etched into the substrate, preferablythrough the thickness of conducting layer 32, so as to insulate thetransducer element from other portions of the substrate which mayinclude other electrical components such as other transducer elementsetched into the substrate.

[0082] According to a specific embodiment, the width of insulatingchamber 36 is about 100 μm. As shown, insulating chamber 36 is etchedinto the substrate so as to form a wall 38 of a predetermined thicknessenclosing cavity 24, and a conducting line 40 integrally made with wall38 for connecting the transducer element to another electronic componentpreferably etched into the same substrate, or to an external electroniccircuit.

[0083] Upper electrode 28 and lower electrode 30 are preferablyprecisely shaped, so as to cover a predetermined area of piezoelectriclayer 26. Electrodes 28 and 30 may be deposited on the upper and lowersurfaces of piezoelectric layer 26, respectively, by using variousmethods such as vacuum deposition, mask etching, painting, and the like.

[0084] Lower electrode 30 is preferably made as an integral part of asubstantially thin electrically conducting layer 42 disposed onelectrically conducting layer 32. Preferably, electrically conductinglayer 42 is made of a Nickel-Copper alloy and is attached toelectrically conducting layer 32 by means of a sealing connection 44.Sealing connection 44 may be made of chemical or physical metal vapourdeposition (CVD or PVD) indium. According to a preferred configuration,sealing connection 44 may feature a thickness of about 10 μm, such thatthe overall height of wall 38 of cavity 24 is about 20-25 μm.

[0085] Preferably, cavity 24 is etched or drilled into the substrate byusing conventional printed-circuit photolithography methods.Alternatively, cavity 24 may be etched into the substrate by usingVLSI/micro-machining technology or any other suitable technology. Cavity24 preferably includes a gas such as air. The pressure of gas withincavity 24 may be specifically selected so as to predetermine thesensitivity and ruggedness of the transducer as well as the resonantfrequency of layer 26.

[0086] Piezoelectric layer 26 may be made of PVDF or a copolymerthereof. Alternatively, piezoelectric layer 26 is made of asubstantially flexible piezoceramic. Preferably, piezoelectric layer 26is a poled PVDF sheet having a thickness of about 9-28 μm.

[0087] Preferably, the thickness and radius of flexible layer 26, aswell as the pressure within cavity 24, are specifically selected so asto provide a predetermined resonant frequency.

[0088] The use of a substantially flexible piezoelectric layer 26,allows to produce a miniature transducer element whose resonantfrequency is such that the acoustic wavelength is much larger than theextent of the transducer. This enables the transducer to beomnidirectional even at resonance, and further allows the use ofrelatively low frequency acoustic signals which do not suffer fromsignificant attenuation in the surrounding medium.

[0089] The configuration and acoustic properties of such an acoustictransducer and variants thereof as well as general acoustic transductionprinciples are described in detail in U.S. patent application Ser. No.09/000,553 and PCT Publication No. WO 99/34,453 the disclosures of whichare expressly incorporated by reference as if fully set forth herein.

[0090] As mentioned hereinabove, the electrical signal generated byacoustic transducer 20 can directly or indirectly activate the releaseof the molecules from reservoir 20.

[0091] In the direct embodiment of device 10 which is specifically shownin FIG. 4, the electrical signal generated by acoustic transducer 20 iscommunicated directly (via circuitry) to electrodes 21 to therebygenerate the electrical potential.

[0092] It will be appreciated that in such cases, the degree of barrierpermeabilization and as such the degree of drug release can becontrolled by the duration and/or frequency of the acoustic signaland/or its intensity received by acoustic transducer 20.

[0093] It will further be appreciated that in cases where device 10includes a plurality of reservoirs, several acoustic transducers can beutilized such that various activation schemes can be employed.

[0094] For example, device 10 can include a plurality of acoustictransducers 20 each dedicated to a specific reservoir of reservoirs 14.In such a case, each acoustic transducer 20 can function within aspecific frequency range and as such activate release from a specificreservoir 14 only upon reception of an acoustic signal of the specificfrequency of frequency range.

[0095] Such a configuration enables selective activation of specificreservoirs enabling control over the amount and rate of moleculesreleased as well as enabling control over the type of moleculesreleased, in cases where specific molecules are stored within specificreservoirs.

[0096] In the indirect embodiment of device 10 which is specificallyshown in FIG. 5, the electrical signal generated by acoustic transducer20 serves to activate an energy storage device 54 which in turngenerates the electrical potential between electrodes 21.

[0097] In such cases, acoustic transducer 20 preferably forms a part ofan acoustic switch 50 which can be configured as described below.

[0098] As specifically shown in FIG. 6, acoustic switch 50 includes anelectrical circuit 52 configured for performing one or more functions orcommands when activated.

[0099] Acoustic switch 50 further includes an energy storage device 54(power source) and an acoustic transducer 20 coupled to electricalcircuit 52 and energy storage device 54.

[0100] In addition, acoustic switch 50 also includes a switch 56, suchas the switch described in the Examples section below, althoughalternatively other switches, such as a miniature electromechanicalswitch and the like (not shown) may be provided.

[0101] Energy storage device 54 may be any of a variety of knowndevices, such as an energy exchanger, a battery and/or a capacitor (notshown). Preferably, energy storage device 54 is capable of storingelectrical energy substantially indefinitely. In addition, energystorage device 54 may be capable of being charged from an externalsource, e.g., inductively, as will be appreciated by those skilled inthe art. In a preferred embodiment, energy storage device 54 includesboth a capacitor and a primary, non-rechargeable battery. Alternatively,energy storage device 54 may include a secondary, rechargeable batteryand/or capacitor that may be energized before activation or use ofacoustic switch 50.

[0102] Acoustic switch 50 operates in one of two modes, a “sleep” or“passive” mode when not in use, and an “active” mode, when commandingelectrical energy delivery from energy storage device 54 to electricalcircuit 52 in order to activate release of molecules from reservoir 14as described hereinabove.

[0103] When in the sleep mode, there is substantially no energyconsumption from energy storage device 54, and consequently, acousticswitch 50 may remain in the sleep mode virtually indefinitely, i.e.,until activated. Thus, acoustic switch 50 may be more energy efficientand, therefore, may require a smaller capacity energy storage device 54than power switching devices that continuously draw at least a smallamount of current in their “passive” mode.

[0104] To activate the acoustic switch, one or more external acousticenergy waves or signals 57 are transmitted until a signal is received byacoustic transducer 20. Upon excitation by acoustic wave(s) 57, acoustictransducer 20 produces an electrical output that is used to close, open,or otherwise activate switch 56. Preferably, in order to achievereliable switching, acoustic transducer 20 is configured to generate avoltage of at least several tenths of a volt upon excitation that may beused as an activation signal to close switch 56.

[0105] As a safety measure against false positives (either erroneousactivation or deactivation), switch 56 may be configured to close onlyupon receipt of an initiation signal followed by a confirmation signal.For example, an activation signal that includes a first pulse followedby a second pulse separated by a predetermined delay may be employed.

[0106] It will be appreciated that in the case of device 10 of thepresent invention, the use of a confirmation signal may be particularlyadvantageous since it can prevent unintentional release of drugs.

[0107] In addition to an activation signal, acoustic transducer 20 maybe configured for generating a termination signal in response to asecond acoustic excitation (which may be of different frequency orduration than the activation signal) in order to return acoustic switch50 to its sleep mode.

[0108] For example, once activated, switch 56 may remain closedindefinitely, e.g., until energy storage device 54 is depleted or untila termination signal is received by acoustic transducer 20.Alternatively, acoustic switch 50 may include a timer (not shown), suchthat switch 56 remains closed only for a predetermined time, whereuponit may automatically open, returning acoustic switch 50 to its sleepmode.

[0109] Acoustic switch may also include a microprocessor unit whichserves to interpret the electrical signal provided from acoustictransducer 20 (e.g., frequency thereof) into a signal for switchingswitch 56.

[0110] Such interpretation enables to modulate the duration and strengthof an electrical potential provided within reservoir 14 by simplyvarying the frequency and/or duration and/or intensity modulation of theacoustic signal provided from outside the body.

[0111] Additional acoustic switch configurations which are utilizable bythe present invention are described in U.S. patent application Ser. No.09/690,615 filed Oct. 16, 2000, the disclosure of which is expresslyincorporated by reference as if fully set forth herein.

[0112] Device 10 of the present invention can form a part of a systemfor localized release of, for example, drugs, which is referred toherein as system 100.

[0113] As shown in FIG. 7, system 100 also includes an extracorporealunit 102 which serves for generating an acoustic signal outside thebody, which acoustic signal is received by device 10 implanted withinthe body. Numerous devices capable of generating acoustic signal whichcan serve as extracorporeal unit 102 are known in the art, and as suchno further description thereof is given herein.

[0114] System 100 can be used as follows. A device 10 filled withmolecules is implanted within a specific body tissue. Followingimplantation, extracorporeal unit 102 generates an acoustic signal of apredetermined frequency and/or duration thereby activating release ofthe molecules from device 10 as described hereinabove.

[0115] Thus, the present invention provides a device, system and methoduseful for localized delivery of molecules such as drugs.

[0116] The device of the present invention provides several advantagesover prior art devices such as those described in U.S. Pat. Nos.6,123,861 and 5,797,898. Such advantages are afforded by the acoustictransducer component of the device which functions in converting anacoustic signal into an electrical activation signal.

[0117] In sharp contrast, the device described in U.S. Pat. Nos.6,123,861 and 5,797,898, employs radiofrequency (RF) receivers whichactivate drug release upon reception of an RF signal generated outsidethe body. The use of RF activation is disadvantageous since RF signalsare, at least in part, absorbed by body tissues and are directionallylimited by bulky unidirectional antennas used for reception.

[0118] On the other hand, acoustic transducers, such as the one utilizedby the device of the present invention, are omni-directional receiverswhich do not require antennas and as such do not suffer from structuraland functional limitations which are inherent to RF receivers.

[0119] In addition, acoustic activation requires far less energy than RFactivation since acoustic waves, unlike RF waves, propagate well withinthe aqueous medium which forms a substantial part of body tissues.

[0120] Additional objects, advantages, and novel features of the presentinvention will become apparent to one ordinarily skilled in the art uponexamination of the following examples, which are not intended to belimiting. Additionally, each of the various embodiments and aspects ofthe present invention as delineated hereinabove and as claimed in theclaims section below finds experimental support in the followingexamples.

EXAMPLES Acoustic Switch Circuitry and Function

[0121] Referring again to the drawings, FIG. 8, illustrates an exampleof circuitry and components employed by an acoustic switch 200 which isutilizable by the device of the present invention.

[0122] Switch 200 includes a piezoelectric transducer, or other acoustictransducer such the acoustic transducer described hereinabove (notshown, but connectable at locations piezo + and piezo −), a plurality ofMOSFET transistors (Q1-Q4) and resistors (R1-R4), and switch S1.

[0123] In the switch's “sleep” mode, all of the MOSFET transistors(Q1-Q4) are in an off state. To maintain the off state, the gates of thetransistors are biased by pull-up and pull-down resistors. The gates ofN-channel transistors (Q1, Q3 & Q4) are biased to ground and the gate ofP-channel transistor Q2 is biased to +3V. During this quiescent stage,switch S1 is closed and no current flows through the circuit.

[0124] Therefore, although an energy storage device (not shown, butcoupled between the hot post, labeled with an exemplary voltage of +3V,and ground) is connected to the switch 200, no current is being drawntherefrom since all of the transistors are quiescent.

[0125] When the piezoelectric transducer detects an external acousticsignal, e.g., having a particular frequency such as the transducer'sresonant frequency, the voltage on the transistor Q1 will exceed thetransistor threshold voltage of about one half of a volt. Transistor Q1is thereby switched on and current flows through transistor Q1 andpull-up resistor R2. As a result of the current flow through transistorQ1, the voltage on the drain of transistor Q1 and the gate of transistorQ2 drops from +3V substantially to zero (ground). This drop in voltageswitches on the P-channel transistor Q2, which begins to conduct throughtransistor Q2 and pull-down resistor R3.

[0126] As a result of the current flowing through transistor Q2, thevoltage on the drain of transistor Q2 and the gates of transistors Q3and Q4 increases from substantially zero to +3V. The increase in voltageswitches on transistors Q3 and Q4. As a result, transistor Q3 begins toconduct through resistor R4 and main switching transistor Q4 begins toconduct through the “load,” thereby switching on the electrical circuit.

[0127] As a result of the current flowing through transistor Q3, thegate of transistor Q2 is connected to ground through transistor Q3,irrespective of whether or not transistor Q1 is conducting. At thisstage, the transistors (Q2, Q3 & Q4) are latched to the conductingstate, even if the piezoelectric voltage on transistor Q1 issubsequently reduced to zero and transistor Q1 ceases to conduct. Thus,main switching transistor Q4 will remain on until switch S1 is opened.

[0128] In order to deactivate or open switch 200, switch S1 must beopened, for example, while there is no acoustic excitation of thepiezoelectric transducer. If this occurs, the gate of transistor Q2increases to +3V due to pull-up resistor R2. Transistor Q2 then switchesoff, thereby, in turn, switching off transistors Q3 and Q4. At thisstage, switch 200 returns to its sleep mode, even if switch S1 is againclosed. Switch 200 will only return to its active mode upon receiving anew acoustic activation signal from the piezoelectric transducer.

[0129] It should be apparent to one of ordinary skill in the art thatthe above-mentioned electrical circuit is not the only possibleimplementation of a switch for use with the present invention. Forexample, the switching operation my be performed using a CMOS circuit,which may draw less current when switched on, an electromechanicalswitch, and the like.

[0130] It is appreciated that certain features of the invention, whichare, for clarity, described in the context of separate embodiments, mayalso be provided in combination in a single embodiment. Conversely,various features of the invention which are, for brevity, described inthe context of a single embodiment, may also be provided separately orin any suitable subcombination.

[0131] Although the invention has been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims. All publications, patents and patentapplications mentioned in this specification are herein incorporated intheir entirety by reference into the specification, to the same extentas if each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated herein byreference. In addition, citation or identification of any reference inthis application shall not be construed as an admission that suchreference is available as prior art to the present invention.

What is claimed is:
 1. A device for controlled release of moleculescomprising: (a) a device body having at least one reservoir therein forcontaining the molecules, said at least one reservoir being formed witha barrier impermeable to the molecules thereby preventing releasethereof from said at least one reservoir; and (b) at least one acoustictransducer being attached to, or forming a part of, said device body,said at least one acoustic transducer being for converting an acousticsignal received thereby into an electrical signal, said electricalsignal leading to barrier permeabilization and therefore release of themolecules from said at least one reservoir.
 2. The device of claim 1,further comprising a cathode, and an anode, whereas said electricalsignal generates an electric potential between said cathode and saidanode leading to permeabilization of said barrier and release of themolecules from said at least one reservoir.
 3. The device of claim 2,wherein said anode is attached to or forms at least a part of saidbarrier.
 4. The device of claim 2, wherein said electrical signaldirectly generates said electric potential between said cathode and saidanode.
 5. The device of claim 2, further comprising a power source forgenerating said electric potential between said cathode and said anodeupon receiving said electrical signal from said at least one acoustictransducer.
 6. The device of claim 1, wherein said at least one acoustictransducer serves as an acoustic switch.
 7. The device of claim 1,wherein permeabilization of said barrier is effected by at least partialdisintegration thereof.
 8. The device of claim 1, wherein a type orduration of said electrical signal controls a degree of permeabilizationof said barrier and thus an amount of the molecules released.
 9. Thedevice of claim 1, wherein the device includes a plurality ofreservoirs.
 10. The device of claim 9, wherein the device includes aplurality of acoustic transducers.
 11. The device of claim 10, whereineach of said plurality of acoustic transducers generates an electricalsignal which leads to permeabilization of a barrier of a correspondingreservoir of said plurality of reservoirs.
 12. The device of claim 11,wherein each of said plurality of acoustic transducers is capable ofconverting an acoustic signal of a distinct frequency or frequenciesinto said electrical signal.
 13. The device of claim 9, wherein saidplurality of reservoirs are for containing different types of molecules,different amounts of molecules, or combinations thereof.
 14. The deviceof claim 1, wherein the molecules are drug molecules.
 15. The device ofclaim 1, wherein said at least one acoustic transducer includes: (i) acell member having a cavity; (ii) a substantially flexible piezoelectriclayer attached to said cell member, said piezoelectric layer having anexternal surface and an internal surface, said piezoelectric layerfeaturing such dimensions so as to enable fluctuations thereof at itsresonance frequency upon impinging of an external acoustic wave; and(iii) a first electrode attached to said external surface and a secondelectrode attached to said internal surface.
 16. A device for controlleddrug release comprising: (a) a device body including at least onereservoir being for containing a prodrug form of a drug, said at leastone reservoir being formed with a barrier impermeable to said prodrugthereby preventing release thereof from said at least one reservoir; and(b) at least one acoustic transducer being attached to, or forming apart of said device body, said at least one acoustic transducer beingfor converting an acoustic signal received thereby into an electricalsignal, said electrical signal leading to a conversion of said prodruginto said drug, said drug being capable of traversing said barrierthereby releasing from said at least one reservoir.
 17. The device ofclaim 16, further comprising a cathode, and an anode disposed withinsaid at least one electrode, whereas said electrical signal generates anelectric potential between said cathode and said anode leading to saidconversion of said prodrug into said drug.
 18. The device of claim 16,wherein said anode is attached to or forms at least a part of saidbarrier.
 19. The device of claim 17, wherein said electrical signaldirectly generates said electric potential between said cathode and saidanode.
 20. The device of claim 17, further comprising a power source forgenerating said electric potential between said cathode and said anodeupon receiving said electrical signal from said at least one acoustictransducer.
 21. The device of claim 16, wherein said at least oneacoustic transducer serves as an acoustic switch.
 22. The device ofclaim 16, wherein a type or duration of said electrical signal controlsa degree of said conversion and thus an amount of said drug formed andreleased
 23. The device of claim 16, wherein the device includes aplurality of reservoirs.
 24. The device of claim 16, wherein the deviceincludes a plurality of acoustic transducers.
 25. The device of claim24, wherein each of said plurality of acoustic transducers generates anelectrical signal which leads to said conversion of said prodrug to saiddrug contained in a corresponding reservoir of said plurality ofreservoirs.
 26. The device of claim 25, wherein each of said pluralityof acoustic transducers is capable of converting an acoustic signal of adistinct frequency or frequencies into said electrical signal.
 27. Thedevice of claim 23, wherein said plurality of reservoirs are forcontaining different types of prodrugs, different amounts of prodrugs,or combinations thereof.
 28. The device of claim 16, wherein said atleast one acoustic transducer includes: (i) a cell member having acavity; (ii) a substantially flexible piezoelectric layer attached tosaid cell member, said piezoelectric layer having an external surfaceand an internal surface, said piezoelectric layer featuring suchdimensions so as to enable fluctuations thereof at its resonancefrequency upon impinging of an external acoustic wave; and (iii) a firstelectrode attached to said external surface and a second electrodeattached to said internal surface.
 29. A method of delivering moleculesto a specific body region, the method comprising: (a) implanting withinthe body region a device including: (i) a device body having at leastone reservoir therein containing the molecules, said at least onereservoir being formed with a barrier impermeable to the moleculesthereby preventing release thereof from said at least one reservoir; and(ii) at least one acoustic transducer being attached to, or forming apart of, said device body, said at least one acoustic transducer beingfor converting an acoustic signal received thereby into an electricalsignal, said electrical signal leading to barrier permeabilization andtherefore release of the molecules from said at least one reservoir; and(b) extracorporeally irradiating the body with an acoustic signalthereby causing the subsequent release of the molecules from said atleast one reservoir.
 30. The method of claim 29, wherein said deviceincludes a plurality of reservoirs each containing molecules of aspecific type and each capable of releasing said molecules uponprovision of an acoustic signal of a specific frequency or frequencies,such that a frequency content of said acoustic signal determines a typeof said molecules released.
 31. The method of claim 29, wherein afrequency content or duration of said acoustic signal controls a degreeof permeabilization of said barrier and thus an amount of the moleculesreleased.
 32. The method of claim 29, wherein said molecules are drugmolecules.
 33. The method of claim 29, wherein said device furtherincludes a cathode, and an anode, whereas said electrical signalgenerates an electric potential between said cathode and said anodeleading to permeabilization of said barrier and release of the moleculesfrom said at least one reservoir.
 34. The method of claim 33, whereinsaid anode is attached to or forms at least a part of said barrier. 35.The method of claim 33, wherein said electrical signal directlygenerates said electric potential between said cathode and said anode.36. The method of claim 33, wherein said device further includes a powersource for generating said electric potential between said cathode andsaid anode upon receiving said electrical signal from said at least oneacoustic transducer.
 37. The method of claim 29, wherein said acoustictransducer serves as an acoustic switch.
 38. A system for localizeddelivery of molecules within the body comprising: (a) an intrabodyimplantable device including: (i) a device body having at least onereservoir therein for containing the molecules, said at least onereservoir being formed with a barrier impermeable to the moleculesthereby preventing release thereof from said at least one reservoir; and(ii) at least one acoustic transducer being attached to, or forming apart of, said device body, said at least one acoustic transducer beingfor converting an acoustic signal received thereby into an electricalsignal, said electrical signal leading to barrier permeabilization andtherefore release of the molecules from said at least one reservoir; and(b) an extracorporeal unit for generating said acoustic signal.
 39. Asystem for localized delivery of molecules within the body comprising:(a) an intrabody implantable device including: (i) a device bodyincluding at least one reservoir being for containing a prodrug form ofa drug, said at least one reservoir being formed with a barrierimpermeable to said prodrug thereby preventing release thereof from saidat least one reservoir; and (ii) at least one acoustic transducer beingattached to, or forming a part of said device body, said at least oneacoustic transducer being for converting an acoustic signal receivedthereby into an electrical signal, said electrical signal leading to aconversion of said prodrug into said drug, said drug being capable oftraversing said barrier thereby releasing from said at least onereservoir; and (b) an extracorporeal unit for generating said acousticsignal.
 40. A method of fabricating a device for controllable release ofmolecules, the method comprising: (a) providing a substrate; (b)configuring said substrate with at least one reservoir; (c) capping saidat least one reservoir with a cap material which acts as an impermeablebarrier to the molecules, said material becoming permeable to themolecules following generation of an electrical potential in or aroundsaid at least one reservoir; and (d) providing an inlet port for fillingsaid at least on reservoir with the molecules, said inlet being sealablefollowing said filling, thereby generating the device for controllablerelease of molecules.
 41. The method of claim 40, further comprising thestep of: (e) attaching to, or fabricating within, said substrate, atleast one acoustic transducer, said at least one acoustic transducerbeing for generating an electrical signal from an acoustic signalreceived thereby, said electrical signal leading to generation of saidelectrical potential in or around said at least one reservoir.
 42. Themethod of claim 41, wherein said at least one acoustic transducerincludes: (i) a cell member having a cavity; (ii) a substantiallyflexible piezoelectric layer attached to said cell member, saidpiezoelectric layer having an external surface and an internal surface,said piezoelectric layer featuring such dimensions so as to enablefluctuations thereof at its resonance frequency upon impinging of anexternal acoustic wave; and (iii) a first electrode attached to saidexternal surface and a second electrode attached to said internalsurface.
 43. The method of claim 40, wherein step (b) is effected byetching said substrate.